I was lucky enough to come by nearly 700 used IFB wedges this fall at a Raku workshop in Southern Wisconsin that were in great shape and in January finished a 22 cuft propane fired kiln that has me pretty excited! I fired my first load last week over 7 hours to cone 10 and feel pretty happy over all with the process and outcome. Over the previous couple of years I read 3 different books and oodles of posts and articles on kiln bulding including Nils Lou and Olson's classic before taking the project on. I spent several weeks agonizing over design and layout concerns but in the end going out into the cold and setting down bricks was the thing that finally allowed me to overcome fear and inertia. The fear of buring my shop down was a motivator to be meticulous as well... I have learned a tonne in the process and may tear it down and build it again this summer! Probably not though...
Fortunately the wedges were all pretty much all the same with a minimal slope that made prefect little wall bricks when paired with matching wedges, and it gives the brick lines of the wall a wavey wonkey look I am very fond of. After 3 rows of these I spent more time trying to match the ends to make the "waves" consistent.
When I had finalized the chamber dimensions (mostly) and the design I spoke with Mr Ward at Ward Burners (invaluable resource) and checked my math on BTU/Hr input and am using 2 MR 100 burners with Baso safety and high pressure pilot and fired at 4.5 psi peak to hit cone 10. My chimney is 6 feet of brick going into Class A double wall stainless chimney pipe. The opening of the roof the pipe passes through is lined with 2inch 2300 degree cerablanket. I had cut it for the exit flue I was using when I had a fling with an old 10cuft Torchbearer updraft gas kiln. I did check the melting temp of stainless steel the morning of the first firing to be safe since the Class A pipe is rated only to 2000 degrees. I tried to make the base of the chimney have some thermal mass to take some energy out of the exhaust, but I suspect at peak temp for a cone 10 firing I am exceeding the rated temp by some couple of hundred degrees.
So Anyway, I made a light saber, now am I a Jedi?

Super
This is what's its about- gathering materials and using what you have -thinking outside the box. This looks like a sweet little kiln. I'm sure now you can second guess what if but thats all part of the process and the next one made will be a natural learning progression building on what you have learned.
Thank you for posting these photos-so few folks take your path and its such a good one as it completes the ceramic circle at least for me and in my life. Making kilns is another step in the whole process.
Firing your own work in your kiln-well you know now what's thats about now. Congratulations on a great job well done.

Very nice looking craftsmanship and design work ....particulary for a "first build". Impressive.

I'm a little concerned about the clearances in the area of the roof penetration point.... the place that about 90% of fuel fired kiln fires start. Even if the first few firings are OK... wood pyrolizes over time. This slowly lowers the ignition point. What was seemingly "fine" 20 firings ago.... now catches on fire. This usually happens after the kiln has been shut down at the end of the firing... and the potter has stopped monitoring the kiln.

There looks to be some structural wood very close laterally to the double wall stainless section. I think it is less than the recommended distance for even a gas fired furnace type appliance which has a lower general effluent temperature.

Also ..... make sure that the fiber you mentioned at the actual penetration point is not tight up against the outsdide of the metal pipe.... you need some air space between them. Otherwise you'll raise the temperature of the both layers of stainless a lot...possibly to the more rapid failure point.

And it is best if you design the roof penettration flashing syustem so that there is cold room air circulationg up and out along the surface of the chimney and to the exterior. So as not to form a dead air poctet in the rafter/joist area at the top of the roof penetration surrounding the metal chimney. It then becomes self cooling and self venting due to the hot boyant air that is formed there.

If the fiber is right against the wood, AND if you don;t vent the area well.... you can actually RAISE the temperature of the wood rather than protect it. An air space with circulating air is again the way to go with this.

Very nice looking craftsmanship and design work ....particulary for a "first build". Impressive.

I'm a little concerned about the clearances in the area of the roof penetration point.... the place that about 90% of fuel fired kiln fires start. Even if the first few firings are OK... wood pyrolizes over time. This slowly lowers the ignition point. What was seemingly "fine" 20 firings ago.... now catches on fire. This usually happens after the kiln has been shut down at the end of the firing... and the potter has stopped monitoring the kiln.

There looks to be some structural wood very close laterally to the double wall stainless section. I think it is less than the recommended distance for even a gas fired furnace type appliance which has a lower general effluent temperature.

Also ..... make sure that the fiber you mentioned at the actual penetration point is not tight up against the outsdide of the metal pipe.... you need some air space between them. Otherwise you'll raise the temperature of the both layers of stainless a lot...possibly to the more rapid failure point.

And it is best if you design the roof penettration flashing syustem so that there is cold room air circulationg up and out along the surface of the chimney and to the exterior. So as not to form a dead air poctet in the rafter/joist area at the top of the roof penetration surrounding the metal chimney. It then becomes self cooling and self venting due to the hot boyant air that is formed there.

If the fiber is right against the wood, AND if you don;t vent the area well.... you can actually RAISE the temperature of the wood rather than protect it. An air space with circulating air is again the way to go with this.

best,

....................john

Thanks for the reply and positive feedback. Though it looks tight there is 3 inches on either side of the header 2x4 originally placed there to hold the old vent straps. This spring I will pull those and frame a larger opening for the stack. The other bit of scrap in the back was just a temporary support I used to secure the SS stack (heavy in 3 foot lengths) while I sorted out what was going on below and finished fabricating the steel adaptor/reducer. There is a good 2 inches of space around the deck sheeting of the roof, but the fiber is loosly in contact with both. It probably makes sense to just pull the fiber and allow cool air to be drawn through the space by convection. I do need to replace the roof flashing this summer as the old flashing is still there, but it was frozen down and there was 8 inches of snow on the roof and damn I wanted to fire that kiln! So I just cut some relief slots in the flashing and pushed the new stack through knowing it was going to come down in spring providing it did not burn down first. I like the idea of creating some cool air flow around the stack and in spring can increase the roof sheeting clearance further and can make a flashing system designed to promote upward air circulation during a firing.My scary moment was the day I finished the sprung arch roof and needed to remove the arch former. As I worked up the courage to take out the former supports it occured to me that there was enough brick potentially falling on my head that It would probably hurt pretty bad so I left my wife a note directing her where to find my body if she got home and I was not inside. Fortunately after I finished celebrating the non-failure of the arch roof (much jubilant shouting and toasting to my clever Roman guides) I remembered to dispose of the note, though I did try to explain to her the magnitude of my accomplishment. Pulling the arch former is a real act of faith.

My scary moment was the day I finished the sprung arch roof and needed to remove the arch former. As I worked up the courage to take out the former supports it occured to me that there was enough brick potentially falling on my head that It would probably hurt pretty bad so I left my wife a note directing her where to find my body if she got home and I was not inside. Fortunately after I finished celebrating the non-failure of the arch roof (much jubilant shouting and toasting to my clever Roman guides) I remembered to dispose of the note, though I did try to explain to her the magnitude of my accomplishment. Pulling the arch former is a real act of faith.

My scary moment was the day I finished the sprung arch roof and needed to remove the arch former. As I worked up the courage to take out the former supports it occured to me that there was enough brick potentially falling on my head that It would probably hurt pretty bad so I left my wife a note directing her where to find my body if she got home and I was not inside. Fortunately after I finished celebrating the non-failure of the arch roof (much jubilant shouting and toasting to my clever Roman guides) I remembered to dispose of the note, though I did try to explain to her the magnitude of my accomplishment. Pulling the arch former is a real act of faith.

Thanks for starting off my day with a laugh!

Jim

I can relate to the caution and planning. The first time I went to fire my Raku kiln, I told my wife, that if she heard any loud "Booms" to call the appropriate authorities. This was despite the fact, that I was fairly certain, I had built it and would fire it correctly.

There was also another time, not related to ceramics, that I had my wife, come watch as I used a voltmeter to check a 220 dryer outlet. I knew, that the insulated probes, should protect me from a shock. But after being taught my whole life, to not, jam things into outlets, it's tough to get over. Especially, with 220 volts, and plenty of amps to greet me, if I was wrong.

I am starting the retro fitting of an electric kiln to a downdraft gas kiln.I need some advice.

I am posting the pictures of the bottom part of the kiln with a chmney.
The cheminy size looks ok?
I am not sure if the burner port holes size are enough big.
Any comments?
Thank you! Cheminy.jpg55.85KB101 downloadsBurner port.jpg48.37KB89 downloads

Dear Beliz,
My personal opinion is you need to double the insulation. Remove the steel jacket and add a couple of inches of fiber.
Then replace the jacket. Insulation is really important for retaining heat and being efficient.

Beliz
Unless your final Temperature is going to be very low I agree with Marcia on above post. You need more insulation on outer walls.After wrapping more fiber around walls replace jacket. It will not go all the way around so add some sheet metal and longer hose clamps to hold it back in place.
Mark

The Olympic updraft gas kilns don't have extra insulation, do they? If you've got enough power in the burners, it'll work. But those Olympics usually have 4-6 venturi burners, so unless yours are big ones, you'll need more insulation. As for the burner ports, the port should be about 1/2" bigger all around than the burner tip. The tip should be a distance from the port equal to the radius of the burner tip (2" tip = 1" from port).

But those Olympics usually have 4-6 venturi burners, so unless yours are big ones, you'll need more insulation.

Thank you for the reply and advice to all..

The kiln is a Skutt and the burners are MR750 Venturi.I first got an advice of using 4 burners .After talking with Ward they told me that I don't need 4 burners for 9cb feet kiln.I took their advice and I am using 2 burners now.I am planning to do low firings first but I want to have my options open as well if I need to do high firings therefore it is a good idea to go around the kiln w fiber blanket.How thick should be the fiber blanket?

But those Olympics usually have 4-6 venturi burners, so unless yours are big ones, you'll need more insulation.

Thank you for the reply and advice to all..

The kiln is a Skutt and the burners are MR750 Venturi.I first got an advice of using 4 burners .After talking with Ward they told me that I don't need 4 burners for 9cb feet kiln.I took their advice and I am using 2 burners now.I am planning to do low firings first but I want to have my options open as well if I need to do high firings therefore it is a good idea to go around the kiln w fiber blanket.How thick should be the fiber blanket?

How tall the chimney should be?

If you decide to do high fires I would add at least 2 inches of medium density-6# fiber-its sold in 4-6-8# if I recallI would build the stack at least 6 feet past kiln top as a minimum-I'm a fan of taller stacks as they suck better.Mark

But those Olympics usually have 4-6 venturi burners, so unless yours are big ones, you'll need more insulation.

Thank you for the reply and advice to all..

The kiln is a Skutt and the burners are MR750 Venturi.I first got an advice of using 4 burners .After talking with Ward they told me that I don't need 4 burners for 9cb feet kiln.I took their advice and I am using 2 burners now.I am planning to do low firings first but I want to have my options open as well if I need to do high firings therefore it is a good idea to go around the kiln w fiber blanket.How thick should be the fiber blanket?

How tall the chimney should be?

If you decide to do high fires I would add at least 2 inches of medium density-6# fiber-its sold in 4-6-8# if I recallI would build the stack at least 6 feet past kiln top as a minimum-I'm a fan of taller stacks as they suck better.Mark

Picture of my converted cone 10 electric to gas updraft kiln using 1 inch 8# density fiber outside, ITC coated inside. 2 forced air burners, top and bottom to even out the heat. Top burner can be placed on lower or top collar depending on ware load. Couple of pictures to show results of my firing.

I converted a 10 CuFt Olympic Torchbearer in a similar fashion and I used 2 MR 750 burners on high pressure propane and never had to exceed 5 PSI to fire to cone 10. I could easily have run most firings in 6 hours or even less if I wanted to as the the MR 750 has more than ample capacity on HP propane (BTU/Hr) to fire a 10 CuFt kiln even with just 3 inches of IFB. I never added any insulation except at the base as it was hard brick (a terrible heat sink-probably eating 20K BTU/Hr per firing). My intent was more to explore the possibility of converting to down draft and really wanted to even out the firing and have more predicatable and even reduction. I never planned to fire long term with it as I new I was going to build a more permanent kiln eventually. My chimney cross section area was 42.25 Sq inches (107 cmsq) but I was nearly 9 feet tall to get suffecient draft, and even that was less than I wanted. Simon Leach fires a salvaged electric 10cuft kiln with 2 weed burners from the hardware store and no additional insulation with a smaller chimney diameter and a stack height equal to the ht of the kiln - though for the life of me I am not sure why it works as well as it does. I added some height to my chimney because the flame path on exit traversed the bottom of the kiln, Simons ported directly into a chimney inside the chamber. I did coat the inside with HTC 100. If you have enough draft it looks like you have the needed energy input and you should be able to fire to cone 10 with your set up. It will not be very effecient of course, the addition of Cerawool to the exterior of the chanber and lid will improve on that significantly and represent a cost savings over time. I was using 100 lb tanks and they hold 2.2 million BTU (about 23 gallons), and I estimated I needed about 350,000 BTU per hour for the 3 inch IFB torchbearer to hit cone 10 in 6 to 8 hours of firing. Most firings were done in under 8 hours and did not quite use a full 100 lb tank (ie 23 gallons of propane). It was pretty wastefull. Interestingly when I was designing mynew kiln I came up with nearly the same BTU/Hr (320K) to make cone 10 in 8 hours, but it is more than twice the cubic feet because.
When I was in the contemplation stage of this build I went to see a kiln near me that a friend said the owner would let us use if we could get it to fire. When we checked it out it was nearly 40 cubic feet and of all hard brick. She was trying to fire it on 4 MR 750 burners running 8 in wc natural gas. After a failed first firing she added more hard bring to the interior to reduce the chanber size, which added more thermal mass, but did reduce the input needed slightly. The chimney size and hieght looked right, but when I ran the calculations the kiln as it stood would have needed over 2 million BTU per hour to fire to cone 10 in 8 to 10 hours! If we could have provided that energy input it probalby would have fired, but who could afford it? not to mention what temperature the exterior of the kiln might have hit over that time.

I converted a 10 CuFt Olympic Torchbearer in a similar fashion and I used 2 MR 750 burners on high pressure propane and never had to exceed 5 PSI to fire to cone 10. I could easily have run most firings in 6 hours or even less if I wanted to as the the MR 750 has more than ample capacity on HP propane (BTU/Hr) to fire a 10 CuFt kiln even with just 3 inches of IFB. I never added any insulation except at the base as it was hard brick (a terrible heat sink-probably eating 20K BTU/Hr per firing). My intent was more to explore the possibility of converting to down draft and really wanted to even out the firing and have more predicatable and even reduction. I never planned to fire long term with it as I new I was going to build a more permanent kiln eventually. My chimney cross section area was 42.25 Sq inches (107 cmsq) but I was nearly 9 feet tall to get suffecient draft, and even that was less than I wanted. Simon Leach fires a salvaged electric 10cuft kiln with 2 weed burners from the hardware store and no additional insulation with a smaller chimney diameter and a stack height equal to the ht of the kiln - though for the life of me I am not sure why it works as well as it does. I added some height to my chimney because the flame path on exit traversed the bottom of the kiln, Simons ported directly into a chimney inside the chamber. I did coat the inside with HTC 100. If you have enough draft it looks like you have the needed energy input and you should be able to fire to cone 10 with your set up. It will not be very effecient of course, the addition of Cerawool to the exterior of the chanber and lid will improve on that significantly and represent a cost savings over time. I was using 100 lb tanks and they hold 2.2 million BTU (about 23 gallons), and I estimated I needed about 350,000 BTU per hour for the 3 inch IFB torchbearer to hit cone 10 in 6 to 8 hours of firing. Most firings were done in under 8 hours and did not quite use a full 100 lb tank (ie 23 gallons of propane). It was pretty wastefull. Interestingly when I was designing mynew kiln I came up with nearly the same BTU/Hr (320K) to make cone 10 in 8 hours, but it is more than twice the cubic feet because.When I was in the contemplation stage of this build I went to see a kiln near me that a friend said the owner would let us use if we could get it to fire. When we checked it out it was nearly 40 cubic feet and of all hard brick. She was trying to fire it on 4 MR 750 burners running 8 in wc natural gas. After a failed first firing she added more hard bring to the interior to reduce the chanber size, which added more thermal mass, but did reduce the input needed slightly. The chimney size and hieght looked right, but when I ran the calculations the kiln as it stood would have needed over 2 million BTU per hour to fire to cone 10 in 8 to 10 hours! If we could have provided that energy input it probalby would have fired, but who could afford it? not to mention what temperature the exterior of the kiln might have hit over that time.

My first firing was about 10 years ago, no fiber, one forced air burner, cone 10 in 4 hours. It was too fast, unlike the Olympic Torchbearer the top was 2 cones cooler. Over the years I added fiber, another burner and two collars. I added fiber to slow the cooling for better glaze colors. Adding the second burner at the top evens out the firing. The forced air burner are very efficient. I now fire in about 7 hours to cone 10 with about 9 gallons of propane.